import java.io.*; import java.util.*; public class Main { static int n; static ArrayList> graph = new ArrayList<>(); static int x; static long ans = 0; static final int MOD = 1000000007; public static void main(String[] args) throws Exception { Scanner sc = new Scanner(); n = sc.nextInt(); int m = sc.nextInt(); x = sc.nextInt(); for (int i = 0; i < n; i++) { graph.add(new ArrayList<>()); } UnionFindTree uft = new UnionFindTree(n); for (int i = 0; i < m; i++) { int left = sc.nextInt() - 1; int right = sc.nextInt() - 1; int cost = sc.nextInt(); if (uft.same(left, right)) { continue; } uft.unite(left, right); graph.get(left).add(new Path(right, cost)); graph.get(right).add(new Path(left, cost)); } getCount(0, 0); System.out.println(ans); } static long getCount(int idx, int p) { long count = 1; for (Path y : graph.get(idx)) { if (y.idx == p) { continue; } long tmp = getCount(y.idx, idx); ans += (n - tmp) * tmp % MOD * pow(x, y.value) % MOD; ans %= MOD; count += tmp; } return count; } static long pow(long x, int p) { if (p == 0) { return 1; } else if(p % 2 == 0) { return pow(x * x % MOD, p / 2); } else { return pow(x, p - 1) * x % MOD; } } static class Path { int idx; int value; public Path(int idx, int value) { this.idx = idx; this.value = value; } } static class UnionFindTree { int[] parent; public UnionFindTree(int size) { parent = new int[size]; for (int i = 0; i < size; i++) { parent[i] = i; } } public int find(int x) { if (parent[x] == x) { return x; } else { return parent[x] = find(parent[x]); } } public boolean same(int x, int y) { return find(x) == find(y); } public void unite(int x, int y) { if (!same(x, y)) { parent[find(x)] = find(y); } } } } class Scanner { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); StringTokenizer st = new StringTokenizer(""); public Scanner() throws Exception { } public int nextInt() throws Exception { return Integer.parseInt(next()); } public long nextLong() throws Exception { return Long.parseLong(next()); } public double nextDouble() throws Exception { return Double.parseDouble(next()); } public String next() throws Exception { if (!st.hasMoreTokens()) { st = new StringTokenizer(br.readLine()); } return st.nextToken(); } }